They help the people that write them $$$

Self help books are good for people who are at a point where they are ready to change a issue but need a new schema (or way of thinking) to act as a structure for that change. When these conditions are met, a self help book can offer a life-changing piece of information. But, when the person then believes that it was the information itself (rather then their own internal readiness) that caused the change in their emotional state, they may continue to seek out answers in books. Usually they are not quite satisfied and do not get the results they first experienced. They may become overly focused on finding "the answers" in new books. The books themselves are usually neutral or positive influences in peoples lives it is only when people mis-attribute their emotional improvement, and thereby dis-empower themselves, that books can become an emotional crutch instead of an aid.

People sometimes don't know the difference between reading something and really learning something. As Einstein said, experience is the only source of knowledge and also said knowledge is not information. What real changes are there in your mind when you read something? Next to none, except maybe a feeling of.. now i get it. But you really don't. To learn you really got to experience something. Self help books might offer temporary solutions or intellgent reasonings, but I think the only ones that would help would be those which lead you into an effort to change yourself by yourself. Some books probly admit that the book itself is useless without you creating the change.